Protective coating for plasma dicing

ABSTRACT

The present invention provides a method for an improved protective coating for plasma dicing a substrate. A work piece having a support film, a frame and the substrate, the substrate having a top surface and a bottom surface, the top surface of the substrate having a plurality of device structures and a plurality of street areas is provided. The work piece is formed by adhering the substrate to a support film and then mounting the substrate with the support film to a frame. A composite material coating having a matrix component and a filler component is applied to the top surface of the substrate. The filler component has a plurality of particles. The composite material coating is removed from at least one street area to expose the street area. The exposed street area is plasma etched. The composite material coating is removed from the top surface of the substrate.

CROSS REFERENCES TO RELATED APPLICATIONS

This application claims priority from and is related to commonly ownedU.S. Provisional Patent Application Ser. No. 63/045,517 filed Jun. 29,2020, entitled: IMPROVED PROTECTIVE COATING FOR PLASMA DICING, thisProvisional Patent Application incorporated by reference herein.

FIELD OF THE INVENTION

The invention relates to the use of a plasma apparatus for the formationof individual device chips from a semi-conductor substrate, and inparticular to an improved method for coating substrates that are plasmaetched into individual die.

BACKGROUND OF THE INVENTION

Semi-conductor devices are fabricated on substrates which are in theform of thin wafers. Silicon is commonly used as the substrate material,but other materials, such as III-V compounds (for example GaAs and InP)are also used. In some instances (for example, the manufacture of LED's)the substrate is a sapphire or silicon carbide wafer on which a thinlayer of a semi-conducting material is deposited. The size of suchsubstrates ranges from two inches and three inches up to two hundredmillimeters and three hundred millimeters diameter and many standardsexist (e.g., SEMI) to describe such substrate sizes.

After fabrication on the substrate, the individual devices (die orchips) are separated from each other prior to packaging or beingemployed in other electronic circuitry. For many years, mechanical meanshave been used to separate the die from each other. Such mechanicalmeans have included breaking the wafer along scribe lines aligned withthe substrate crystal axis or by using a high speed diamond saw to sawinto or through the substrate in a region (streets) between the die.More recently, lasers have been used to facilitate the scribing process.

Recently plasma etching techniques have been proposed as a means ofseparating die and overcoming some of these limitations. After devicefabrication, the substrate is masked with a suitable mask material,leaving open areas between the die. The masked substrate is thenprocessed using a reactive gas plasma which etches the substratematerial exposed between the die. However, the reactive gas plasma alsoetches the mask material. For thicker substrates, the selectivity of theetching of the substrate material to the mask material needs to beimproved.

Therefore, what is needed is an improved protective film that has ahigher selectivity of etching in the reactive gas plasma to thesubstrate material.

Nothing in the prior art provides the benefits attendant with thepresent invention.

Therefore, it is an object of the present invention to provide animprovement which overcomes the inadequacies of the prior art devicesand which is a significant contribution to the advancement to the dicingof semiconductor substrates using a plasma etching apparatus.

Another object of the present invention is to provide a method for animproved protective coating for plasma dicing a substrate, the methodcomprising: providing a work piece having a support film, a frame andthe substrate, the substrate having a top surface and a bottom surface,the top surface of the substrate having a plurality of device structuresand a plurality of street areas; applying a composite material coatingto the top surface of the substrate; removing said composite materialcoating from at least one street area to expose the street area; plasmaetching the exposed street area; and removing said composite materialcoating from the top surface of the substrate.

Yet another object of the present invention is to provide a method foran improved protective coating for plasma dicing a substrate, the methodcomprising: providing a work piece having a support film, a frame andthe substrate, the substrate having a top surface and a bottom surface,the top surface of the substrate having a plurality of device structuresand a plurality of street areas; applying a composite material coatingto the top surface of the substrate, said composite material coatinghaving a matrix component and a filler component; removing saidcomposite material coating from at least one street area to expose thestreet area; plasma etching the exposed street area; and removing saidcomposite material coating from the top surface of the substrate.

Still yet another object of the present invention is to provide a methodfor an improved protective coating for plasma dicing a substrate, themethod comprising: providing a work piece having a support film, a frameand the substrate, the substrate having a top surface and a bottomsurface, the top surface of the substrate having a plurality of devicestructures and a plurality of street areas; applying a compositematerial coating to the top surface of the substrate, said compositematerial coating having a matrix component and a filler component, saidfiller component having a plurality of particles; removing saidcomposite material coating from at least one street area to expose thestreet area; plasma etching the exposed street area; and removing saidcomposite material coating from the top surface of the substrate.

The foregoing has outlined some of the pertinent objects of the presentinvention. These objects should be construed to be merely illustrativeof some of the more prominent features and applications of the intendedinvention. Many other beneficial results can be attained by applying thedisclosed invention in a different manner or modifying the inventionwithin the scope of the disclosure. Accordingly, other objects and afuller understanding of the invention may be had by referring to thesummary of the invention and the detailed description of the preferredembodiment in addition to the scope of the invention defined by theclaims taken in conjunction with the accompanying drawings.

SUMMARY OF THE INVENTION

The present invention describes a charged particle source for arcprevention and stable operation of ion source in processing ofdiamond-like carbon (DLC) films.

Another feature of the present invention is to provide a method for animproved protective coating for plasma dicing a substrate. The substratecan have a semiconducting layer such as Silicon and/or the substrate canhave a III-V layer such as GaAs. A work piece having a support film, aframe and the substrate, the substrate having a top surface and a bottomsurface, the top surface of the substrate having a plurality of devicestructures and a plurality of street areas is provided. The work pieceis formed by adhering the substrate to a support film and then mountingthe substrate with the support film to a frame. The support film canhave a polymer layer and/or a conductive layer. The support film can bestandard dicing tape. The frame can have a conductive layer and/or ametal layer. A composite material coating is applied to the top surfaceof the substrate. The composite material coating can further comprise amatrix component and a filler component. The matrix component canfurther comprise a carbon containing material and/or a polymer material.The matrix component can be water soluble. The matrix component canfurther comprise a poly acrylic acid. The matrix component can furthercomprise dextran. The matrix component can further comprise a polymethacrylic acid. The matrix component can further comprise a polyacrylamide. The matrix component can further comprise a poly ethyleneimine. The matrix component can further comprise a poly vinyl alcohol.The filler component cannot be water soluble. The filler component canfurther comprise a carbon containing material. The matrix component canbe selected from the group consisting of graphite, diamond and siliconcarbide. The filler component can further comprise a silicon containingmaterial. The matrix component can be selected from the group consistingof silicon nitride, silicon dioxide, silicon oxynitride and siliconcarbide. The filler component can further comprise particles. Thecomposite material coating is removed from at least one street area toexpose the street area. The exposed street area is plasma etched. Thecomposite material coating is removed from the top surface of thesubstrate.

Yet another feature of the present invention is to provide a method foran improved protective coating for plasma dicing a substrate. Thesubstrate can have a semiconducting layer such as Silicon and/or thesubstrate can have a III-V layer such as GaAs. A work piece having asupport film, a frame and the substrate, the substrate having a topsurface and a bottom surface, the top surface of the substrate having aplurality of device structures and a plurality of street areas isprovided. The work piece is formed by adhering the substrate to asupport film and then mounting the substrate with the support film to aframe. The support film can have a polymer layer and/or a conductivelayer. The support film can be standard dicing tape. The frame can havea conductive layer and/or a metal layer. A composite material coatinghaving a matrix component and a filler component is applied to the topsurface of the substrate. The matrix component can further comprise acarbon containing material and/or a polymer material. The matrixcomponent can be water soluble. The matrix component can furthercomprise a poly acrylic acid. The matrix component can further comprisedextran. The matrix component can further comprise a poly methacrylicacid. The matrix component can further comprise a poly acrylamide. Thematrix component can further comprise a poly ethylene imine. The matrixcomponent can further comprise a poly vinyl alcohol. The fillercomponent cannot be water soluble. The filler component can furthercomprise a carbon containing material. The matrix component can beselected from the group consisting of graphite, diamond and siliconcarbide. The filler component can further comprise a silicon containingmaterial. The matrix component can be selected from the group consistingof silicon nitride, silicon dioxide, silicon oxynitride and siliconcarbide. The filler component can further comprise particles. Thecomposite material coating is removed from at least one street area toexpose the street area. The exposed street area is plasma etched. Thecomposite material coating is removed from the top surface of thesubstrate.

Still yet another feature of the present invention is to provide amethod for an improved protective coating for plasma dicing a substrate.The substrate can have a semiconducting layer such as Silicon and/or thesubstrate can have a III-V layer such as GaAs. A work piece having asupport film, a frame and the substrate, the substrate having a topsurface and a bottom surface, the top surface of the substrate having aplurality of device structures and a plurality of street areas isprovided. The work piece is formed by adhering the substrate to asupport film and then mounting the substrate with the support film to aframe. The support film can have a polymer layer and/or a conductivelayer. The support film can be standard dicing tape. The frame can havea conductive layer and/or a metal layer. A composite material coatinghaving a matrix component and a filler component is applied to the topsurface of the substrate. The filler component has a plurality ofparticles. The matrix component can further comprise a carbon containingmaterial and/or a polymer material. The matrix component can be watersoluble. The matrix component can further comprise a poly acrylic acid.The matrix component can further comprise dextran. The matrix componentcan further comprise a poly methacrylic acid. The matrix component canfurther comprise a poly acrylamide. The matrix component can furthercomprise a poly ethylene imine. The matrix component can furthercomprise a poly vinyl alcohol. The filler component cannot be watersoluble. The filler component can further comprise a carbon containingmaterial. The matrix component can be selected from the group consistingof graphite, diamond and silicon carbide. The filler component canfurther comprise a silicon containing material. The matrix component canbe selected from the group consisting of silicon nitride, silicondioxide, silicon oxynitride and silicon carbide. The composite materialcoating is removed from at least one street area to expose the streetarea. The exposed street area is plasma etched. The composite materialcoating is removed from the top surface of the substrate.

The foregoing has outlined rather broadly the more pertinent andimportant features of the present invention in order that the detaileddescription of the invention that follows may be better understood sothat the present contribution to the art can be more fully appreciated.Additional features of the invention will be described hereinafter whichform the subject of the claims of the invention. It should beappreciated by those skilled in the art that the conception and thespecific embodiment disclosed may be readily utilized as a basis formodifying or designing other structures for carrying out the samepurposes of the present invention. It should also be realized by thoseskilled in the art that such equivalent constructions do not depart fromthe spirit and scope of the invention as set forth in the appendedclaims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top down view of a semiconductor substrate illustratingindividual devices separated by streets;

FIG. 2 is a cross-sectional view of a semiconductor substrateillustrating individual devices separated by streets;

FIG. 3 is a cross-sectional view of a semiconductor substrate mounted totape and a frame;

FIG. 4 is a cross-sectional view of a semiconductor substrate mounted totape and a frame being etched by a plasma process;

FIG. 5 is a cross-sectional view of separated semiconductor devicesmounted to tape and a frame;

FIG. 6 is a cross-sectional view of a vacuum processing chamber; and

FIG. 7 is a cross-sectional of a wafer/frame in process position.

Similar reference characters refer to similar parts throughout theseveral views of the drawings.

DETAILED DESCRIPTION OF THE INVENTION

A typical semiconductor substrate after device fabrication isillustrated in FIG. 1 . The substrate (1) has on its surface a number ofareas containing device structures (2) separated by street areas (3) inwhich there are no structures which allows for separation of the devicestructures into individual die. Although silicon is commonly used as asubstrate material, other materials chosen for their particularcharacteristics are frequently employed. Such substrate materialsinclude gallium arsenide and other III-V materials or non-semiconductorsubstrates on which a semi-conducting layer has been deposited.

In the present invention, as is shown in a cross sectional view in FIG.2 , a substrate (1) having a plurality of device structures (2) andstreet areas (3) has been covered with a composite material coating (4).The composite material coating (4) is removed from the street areas (3)to expose the street areas (3) while leaving the device structures (2)protected by the composite material coating (4). Although the devicepattern illustrated shows oblong die, this is not necessary, and theindividual device structures (2) may be any other shape, such ashexagons, as best suits the optimum utilization of the substrate (1).

The substrate (1) is thinned, typically by a grinding process, whichreduces the substrate thickness to a few hundred microns to as thin as50 microns. As is shown in FIG. 3 , the thinned substrate (1) is thenadhered to a tape (5) which in turn is mounted in a rigid frame (6) toform a work piece (1A). The tape (5) is typically made from a Carboncontaining polymer material, and may additionally have a thin conductivelayer applied to its surface. The tape (5) provides support for thethinned substrate (1) which is otherwise too fragile to handle withoutbreakage. It should be noted that the sequence of patterning, thinningand then mounting is not critical and the steps may be adjusted to bestfit the particular devices and substrate and the processing equipmentused.

After mounting the substrate (1) with the tape (5) in the dicing frame(6), the work piece (1A) is transferred into a vacuum processingchamber. Ideally, the transfer module is also under vacuum which allowsthe process chamber to remain at vacuum during transfer, reducingprocessing time and preventing exposure of the process chamber toatmosphere and possible contamination. As shown in FIG. 6 , the vacuumprocessing chamber (10) is equipped with a gas inlet (11), a highdensity plasma source (12) to generate a high density plasma, such as anInductively Coupled Plasma (ICP), a work piece support (13) to supportthe work piece (1A), an RF power source (14) to couple RF power to thework piece (1A) through the work piece support (13) and a vacuum pump(15) for pumping gas from the processing chamber (10). Duringprocessing, the exposed street areas (3) of the substrate (1) are etchedaway using a reactive plasma etch process (7) as shown in FIG. 4 . Thisleaves the devices separated into individual die (8) as shown in FIG. 5. The composite material (4) is removed from the top surface of thesubstrate (1).

The substrate can be plasma processed using techniques well known in thesemiconductor industry. Silicon substrates are generally processed usinga Fluorine based chemistry such as SF₆. SF₆/O₂ chemistry is commonlyused to etch Silicon because of its high rate and anisotropic profile. Adisadvantage of this chemistry is its relatively low selectivity tomasking material for example to photoresist which is 15-20:1. Thus, thepresent invention uses a composite material that has a much higherselectivity than photoresist, i.e. selectivity greater than 100:1.

In one embodiment according to the present invention, the compositematerial coating (that can comprise a matrix component and a fillercomponent) is applied to the top surface of the substrate. The matrixcomponent of the composite material coating can be a carbon containingmaterial and/or a polymer material, e.g., Hogomax which is a watersoluble material. The matrix component of the composite material coatingcan further comprise at least one of the following: poly acrylic acid;dextran; poly methacrylic acid; poly acrylamide; poly ethylene imine; orpoly vinyl alcohol. The filler component of the composite materialcoating can have a carbon containing material based on at least one ofthe following: graphite; diamond; or silicon carbide which can make thefiller component not soluble in water. The filler component of thecomposite material coating can also have a silicon containing materialbased on at least one of the following: silicon nitride; silicondioxide; silicon oxynitride; or silicon carbide.

In another embodiment according to the present invention, the compositematerial coating comprises a matrix component and a filler componentthat is applied to the top surface of the substrate. The matrixcomponent of the composite material coating can be a carbon containingmaterial and/or a polymer material and/or a polymer material, e.g.,Hogomax which is a water soluble material. The matrix component of thecomposite material coating can further comprise at least one of thefollowing: poly acrylic acid; dextran; poly methacrylic acid; polyacrylamide; poly ethylene imine; or poly vinyl alcohol. The fillercomponent of the composite material coating can have a carbon containingmaterial based on at least one of the following: graphite; diamond; orsilicon carbide which can make the filler component not soluble inwater. The filler component of the composite material coating can alsohave a silicon containing material based on at least one of thefollowing: silicon nitride; silicon dioxide; silicon oxynitride; orsilicon carbide.

In another embodiment according to the present invention, the compositematerial coating comprises a matrix component and a filler componentthat is applied to the top surface of the substrate. The fillercomponent of the composite material coating contains a plurality ofparticles. The matrix component of the composite material coating can bea carbon containing material and/or a polymer material and/or a polymermaterial, e.g., Hogomax which is a water soluble material. The matrixcomponent of the composite material coating can further comprise atleast one of the following: poly acrylic acid; dextran; poly methacrylicacid; poly acrylamide; poly ethylene imine; or poly vinyl alcohol. Thefiller component of the composite material coating can have a carboncontaining material based on at least one of the following: graphite;diamond; or silicon carbide which can make the filler component notsoluble in water. The filler component of the composite material coatingcan also have a silicon containing material based on at least one of thefollowing: silicon nitride; silicon dioxide; silicon oxynitride; orsilicon carbide.

In any embodiment of the present invention, the plasma source can be aninductively coupled plasma (ICP) using a planar and/or helical antenna.If a planar ICP is used with the RF coil placed behind the back of theion source, then the anode must not be placed at the back of the source.In this case, the anode can be placed half way into the source, and thebest shape for the anode is a cylindrical shape with the grooved surfacebeing parallel to the plasma chamber walls, or to another conductingplate placed parallel to the chamber wall, with the parallel surfacespacing. Alternatively the ICP can be a resonant source which includeshelicons or can be energized with an RF power supply having an RFfrequency between 100 kHz to 100 MHz. Alternatively, the plasma source30 can be DC powered (e.g., DC Magnetron), a capacitively coupledplasma, a surface wave plasma source, a microwave plasma source (e.g.,ECR source) or a magnetically enhanced or confined plasma source.

In any embodiment of the present invention, the substrate can besemiconductor containing such as a semiconductor substrate or containsan epitaxial layer. The semiconductor substrate can be siliconcontaining e.g., glass or a compound semiconductor e.g., contains agroup III element. The substrate can be a ceramic wafer such asAl-containing e.g., AlTiC or C-containing.

In any embodiment of the present invention, a process gas can beprovided by the gas supply into the processing chamber. The process gascan contain an inert gas e.g., He, Ne, Ar, Xe, Kr.

In any embodiment of the present invention, the optical properties ofthe filler material of the composite material coating can be similar tothe optical properties of the matrix material of the composite materialcoating. Alternatively, the optical properties of the filler materialcan be dissimilar to the optical properties of the matrix material.

In any embodiment of the present invention, the filler component of thecomposite material coating can further comprise particles that can rangein sizes such as less than about one hundred microns or less than aboutone micron as measured in the particles greatest dimension.

In any embodiment of the present invention, the particles of the fillercomponent of the composite material coating can be mono disperse insize. In addition, the particles can each have a similar shape, e.g.,spheres, rods, cubes, etc, or the particles can each have a dissimilarshape.

In any embodiment of the present invention, the particles of the fillercomponent of the composite material coating can be designed to optimizethe absorption of moisture, laser radiation and/or plasma energy. Thiscan be accomplished through material fillers that have these knownattributes.

In any embodiment of the present invention, the composite materialcoating can be removed from the street areas by laser ablation.

In any embodiment of the present invention, the composite materialcoating can be removed from the top surface of the substrate usingwater.

In any embodiment of the present invention, the filler component of thecomposite material coating can have a lower plasma etch rate than thematrix component of the composite material.

The present disclosure includes that contained in the appended claims,as well as that of the foregoing description. Although this inventionhas been described in its preferred form with a certain degree ofparticularity, it is understood that the present disclosure of thepreferred form has been made only by way of example and that numerouschanges in the details of construction and the combination andarrangement of parts may be resorted to without departing from thespirit and scope of the invention.

What is claimed is:
 1. A method for an improved protective coating forplasma dicing a substrate, the method comprising: providing a work piecehaving a support film, a frame and the substrate, the substrate having atop surface and a bottom surface, the top surface of the substratehaving a plurality of device structures and a plurality of street areas;applying a composite material coating to the top surface of thesubstrate, the composite material coating further comprising a matrixcomponent and a filler component, the filler component having a lowerplasma etch rate than the matrix component; removing said compositematerial coating from at least one street area to expose the streetarea; placing the work piece with the at least one exposed street areainto a vacuum chamber; igniting a plasma in the vacuum chamber; plasmaetching the exposed street area with said composite coating over theplurality of device structures; and removing said composite materialcoating from the top surface of the substrate.
 2. The method accordingto claim 1 wherein said matrix component further comprising a carboncontaining material.
 3. The method according to claim 1 wherein saidmatrix component further comprising a polymer.
 4. The method accordingto claim 1 wherein said matrix component is water soluble.
 5. The methodaccording to claim 4 wherein said matrix component further comprising apolyacrylic acid.
 6. The method according to claim 5 wherein said matrixcomponent further comprising dextran.
 7. The method according to claim 6wherein said matrix component further comprising a polymethacrylic acid.8. The method according to claim 7 wherein said matrix component furthercomprising a polyacrylamide.
 9. The method according to claim 8 whereinsaid matrix component further comprising a polyethylene imine.
 10. Themethod according to claim 9 wherein said matrix component furthercomprising a polyvinyl alcohol.
 11. The method according to claim 1wherein said filler component is not water soluble.
 12. The methodaccording to claim 1 wherein said filler component further comprising acarbon containing material.
 13. The method according to claim 12 whereinsaid matrix component is selected from the group consisting of graphite,diamond and silicon carbide.
 14. The method according to claim 1 whereinsaid filler component further comprising a silicon containing material.15. The method according to claim 14 wherein said matrix component isselected from the group consisting of silicon nitride, silicon dioxide,silicon oxynitride and silicon carbide.
 16. The method according toclaim 1 wherein said filler component further comprising particles.